What is the domain 'sd.apple.com' compiled into macOS programs used for?

The domain 'sd.apple.com' is compiled into certain macOS programs. A specific example, in the Perl

module Config.pm can be found the key = value pair, 'mydomain' => 'sd.apple.com'. Well, that is not my domain and it is a real pain to have to continually edit files where it is used. For example, if one is creating a C extension to be used with a Perl module one is writing with h2xs, that domain name is used to define the email address of the user. That's bogus and I can't change it other than by hand editing the file or recompiling Perl. What is Apple using that domain for in macOS? Is my machine communicating with that domain without my knowledge? I'm using 10.13.3 on a Pro.